Field of the Invention
The present invention relates to controlling the activation of a communication apparatus.
Description of the Related Art
In a close-proximity wireless communication system exemplified by NFC (Near Field Communication), communication is typically carried out between an initiator, called a “reader/writer”, and a target, called a “tag”. In an electromagnetic field having a specific frequency, the initiator transmits a modulated signal to the target, and based on the received signal, the target transmits a modulated signal to the initiator.
Communication apparatuses that serve as targets are classified into active types that include an internal power supply for operation, and passive types that do not include an internal power supply and instead obtain operational power for the target itself from the signal received from the initiator. Based on this principle of operation, when the electromagnetic field generated by the initiator is weak, a passive type communication apparatus cannot obtain operational power and thus cannot be activated. Meanwhile, although an active type communication apparatus does not depend on the electromagnetic field generated by the initiator, a system that puts the internal power supply and so on into a suspended state when the apparatus is not communicating is typically used in order to conserve power during long-term operation of the apparatus. When, in the suspended state, the active type communication apparatus receives a signal from an initiator, the internal power supply is activated using the received signal in a manner similar to the passive type and the apparatus supplies its own power. As such, an active type communication apparatus cannot activate the internal power supply when the electromagnetic field generated by the initiator is weak.
In response to this issue, Japanese Patent Laid-Open No. 2011-054093 discloses a method in which an initiator-side communication apparatus initially transmits a signal at a maximum transmission power and a target-side communication apparatus activates an internal power supply upon detecting that signal from the initiator.
However, according to the method disclosed in Japanese Patent Laid-Open No. 2011-054093, the initiator-side communication apparatus carries out a process for transmitting the signal at the maximum transmission power regardless of whether or not the target-side communication apparatus is present, and thus a certain amount of time and processing have been necessary until the actual start of communication.
Having been achieved in light of such problems, the present invention provides a technique for activating a communication partner apparatus while reducing processing carried out up until communication is started.